The field of art to which this invention pertains is the simultaneous hydroprocessing of two hydrocarbonaceous feedstocks. Petroleum refiners often produce desirable products such as turbine fuel, diesel fuel and other products known as middle distillates as well as lower boiling hydrocarbonaceous liquids such as naphtha and gasoline by hydrocracking a hydrocarbon feedstock derived from crude oil, for example. Feedstocks most often subjected to hydrocracking are gas oils and heavy gas oils recovered from crude oil by distillation. A typical heavy gas oil comprises a substantial portion of hydrocarbon components boiling above about 700xc2x0 F., usually at least about 50 percent by weight boiling above 700xc2x0 F. A typical vacuum gas oil normally has a boiling point range between about 600xc2x0 F. and about 1050xc2x0 F.
Hydrocracking is generally accomplished by contacting in a hydrocracking reaction vessel or zone the gas oil or other feedstock to be treated with a suitable hydrocracking catalyst under conditions of elevated temperature and pressure in the presence of hydrogen so as to yield a product containing a distribution of hydrocarbon products desired by the refiner. The operating conditions and the hydrocracking catalysts within a hydrocracking reactor influence the yield of the hydrocracked products.
Although a wide variety of process flow schemes, operating conditions and catalysts have been used in commercial activities, there is always a demand for new hydrocracking methods which provide lower costs and higher liquid product yields and higher quality products. Low conversion per pass is generally more expensive, however, the present invention greatly improves the economic benefits of a low conversion per pass process and demonstrates the unexpected advantages.
U.S. Pat. No. 5,720,872 B1 discloses a process for hydroprocessing liquid feedstocks in two or more hydroprocessing stages, which are in separate reaction vessels and wherein each reaction stage contains a bed of hydroprocessing catalyst. The liquid product from the first reaction stage is sent to a low pressure stripping stage and stripped of hydrogen sulfide, ammonia and other dissolved gases. The stripped product stream is then sent to the next downstream reaction stage, the product from which is also stripped of dissolved gases and sent to the next downstream reaction stage until the last reaction stage, the liquid product of which is stripped of dissolved gases and collected or passed on for further processing. The flow of treat gas is in a direction opposite the direction in which the reaction stages are staged for the flow of liquid. Each stripping stage is a separate stage, but all stages are contained in the same stripper vessel.
U.S. Pat. No. 3,328,290 B1 (Hengstebeck) discloses a two-stage process for the hydrocracking of hydrocarbons in which the feed is pretreated in the first stage.
U.S. Pat. No. 5,114,562 B1 (Haun et al) discloses a process wherein a middle distillate petroleum stream is hydrotreated to produce a low sulfur and low aromatic product employing two reaction zones in series. The effluent from the first reaction zone (desulfurization) is cooled and introduced into a hydrogen stripping zone wherein hydrogen sulfide is removed overhead along with a small amount of hydrocarbons which were in the vapor at conditions present at the top of the stripping zone. The bottom stream from the stripping zone is reheated and introduced into the second reaction zone (aromatic saturation) containing sulfur-sensitive noble metal hydrogenation catalyst. The operating pressure increases and the temperature decreases from the first to the second reaction zones. The desulfurization conditions employed are relatively moderate as only a very limited amount of cracking is desired. It is totally undesired to perform any significant cracking within the second reaction zone. It is specifically desired to minimize the content of heavy product distillate hydrocarbons such as diesel fuel in the vapor phase of the stripping zone.
U.S. Pat. No. 5,980,729 B1 (Kalnes et al) discloses a hydrocracking process wherein a hydrocarbonaceous feedstock and a hot hydrocracking zone effluent containing hydrogen is passed to a denitrification and desulfurization reaction zone to produce hydrogen sulfide and ammonia to thereby clean up the fresh feedstock. The resulting hot, uncooled effluent from the denitrification and desulfurization zone is hydrogen stripped in a stripping zone maintained at essentially the same pressure as the preceding reaction zone with a hydrogen-rich gaseous stream to produce a vapor stream comprising hydrogen, hydrocarbonaceous compounds boiling at a temperature below the boiling range of the fresh feedstock, hydrogen sulfide and ammonia, and a liquid hydrocarbonaceous stream.
U.S. Pat. No. 5,403,469 B1 (Vauk et al) discloses a parallel hydrotreating and hydrocracking process. Effluent from the two processes are combined in the same separation vessel and separated into a vapor comprising hydrogen and a hydrocarbon-containing liquid. The hydrogen is shown to be supplied as part of the feed streams to both the hydrocracking and the hydrotreater.
The present invention is a catalytic hydrocracking process which simultaneously hydroprocesses two feedstocks to provide higher liquid product yields and increase the quality of the liquid products. The process of the present invention provides the yield advantages associated with a low conversion per pass operation without compromising unit economics. In addition, lower capital costs will be realized with the use of the present invention.
In the present invention, a first hydrocarbonaceous feedstock and hydrogen are passed to a denitrification and desulfurization reaction zone to produce a stream which is in turn passed to a hot, high pressure stripper utilizing a hot, hydrogen-rich stripping gas to produce a first vapor stream containing hydrogen, hydrogen sulfide, ammonia and hydrocarbonaceous compounds, and a first liquid stream containing hydrocarbonaceous compounds boiling in the range of the first feedstock. At least a portion of the first liquid stream is passed to a hydrocracking zone. A second hydrocarbonaceous feedstock having an average boiling temperature lower than the first hydrocarbonaceous feedstock in one embodiment is passed into an upper end of the hot, high pressure stripper to serve as reflux and in another embodiment is passed into an intermediate location in the denitrification and desulfurization reaction zone to serve as quench. The vapor stream containing hydrogen and hydrocarbonaceous compounds boiling at a temperature below the first feedstock is introduced into a post-treat hydrogenation reaction zone to saturate at least a portion of the aromatic compounds contained therein. In one embodiment, at least a portion of the second feedstock is vaporized in the hot, high pressure stripper and passes into the post-treat hydrogenation reaction zone to saturate aromatic compounds and thereby improve the quality of the hydrocarbonaceous effluent from the post-treat zone. In another embodiment, the second hydrocarbonaceous feedstock serves as quench and passes through at least a portion of the catalyst in the denitrification and desulfurization reaction zone and is subsequently introduced into the hot, high pressure stripper. At least a portion of the effluent from the post-treat hydrogenation reaction zone is condensed to produce a liquid stream containing hydrocarbonaceous compounds boiling at a temperature below the first feedstock and a vapor stream containing hydrogen and hydrogen sulfide. In a preferred embodiment, at least a portion of the hydrogen sulfide is removed from the second vapor stream before it is recycled to the hydrocracking zone.
In accordance with one embodiment the present invention relates to a process for the simultaneous hydroprocessing of two feedstocks having different boiling ranges which process comprises: (a) passing a first hydrocarbonaceous feedstock and hydrogen to a denitrification and desulfurization reaction zone containing a hydrotreating catalyst and operating at a temperature of about 400xc2x0 F. to about 900xc2x0 F., a pressure from about 500 psig to about 2500 psig, a liquid hourly space velocity from about 0.1 hrxe2x88x921 to about 15 hrxe2x88x921 and recovering a denitrification and desulfurization reaction zone effluent therefrom; (b) passing the denitrification and desulfurization reaction zone effluent directly to a hot, high pressure stripper utilizing a hot, hydrogen-rich stripping gas to produce a first vapor stream comprising hydrogen, hydrogen sulfide, ammonia and hydrocarbonaceous compounds and a first liquid stream comprising hydrocarbonaceous compounds boiling in the range of the first hydrocarbonaceous feedstock; (c) passing at least a portion of the first liquid stream comprising hydrocarbonaceous compounds boiling in the range of the first hydrocarbonaceous feedstock to a hydrocracking zone containing a hydrocracking catalyst and operating at a temperature of about 400xc2x0 F. to about 900xc2x0 F., a pressure from about 500 psig to about 2500 psig, a liquid hourly space velocity from about 0.1 hrxe2x88x921 to about 15 hrxe2x88x921 and recovering a hydrocracking zone effluent therefrom; (d) passing the hydrocracking zone effluent directly to the hot, high pressure stripper to produce a second vapor stream comprising lower boiling hydrocarbonaceous compounds and a second liquid stream; (e) passing at least a portion of the first vapor stream recovered in step (b) and at least a portion of the second vapor stream recovered in step (d) to a post-treat hydrogenation reaction zone; (f) condensing at least a portion of the resulting effluent from the post-treat hydrogenation zone to produce a third liquid stream comprising hydrocarbonaceous compounds boiling at a temperature below the first hydrocarbonaceous feedstock and a third vapor stream comprising hydrogen and hydrogen sulfide; (g) passing a second hydrocarbonaceous feedstock having a lower average boiling point than that of the first hydrocarbonaceous feedstock into an upper end of the hot-high pressure stripper to serve as reflux; (h) passing at least a portion of the third vapor stream to the hydrocracking zone; (i) passing at least a portion of the third vapor stream to the denitrification and desulfurization reaction zone; and (j) passing at least a portion of the third vapor stream to the hot, high pressure stripper.
In accordance with another embodiment the present invention relates to a process for the simultaneous hydroprocessing of two feedstocks having different boiling ranges which process comprises: (a) passing a first hydrocarbonaceous feedstock and hydrogen to a denitrification and desulfurization reaction zone containing a hydrotreating catalyst and operating at a temperature of about 400xc2x0 F. to about 900xc2x0 F., a pressure from about 500 psig to about 2500 psig, a liquid hourly space velocity from about 0.1 hrxe2x88x921 to about 15 hrxe2x88x921 and recovering a denitrification and desulfurization reaction zone effluent therefrom; (b) passing the denitrification and desulfurization reaction zone effluent directly to a hot, high pressure stripper utilizing a hot, hydrogen-rich stripping gas to produce a first vapor stream comprising hydrogen, hydrogen sulfide, ammonia and hydrocarbonaceous compounds and a first liquid stream comprising hydrocarbonaceous compounds boiling in the range of the first hydrocarbonaceous feedstock; (c) passing at least a portion of the first liquid stream comprising hydrocarbonaceous compounds boiling in the range of the first hydrocarbonaceous feedstock to a hydrocracking zone containing a hydrocracking catalyst and operating at a temperature of about 400xc2x0 F. to about 900xc2x0 F., a pressure from about 500 psig to about 2500 psig, a liquid hourly space velocity from about 0.1 hrxe2x88x921 to about 15 hrxe2x88x921 and recovering a hydrocracking zone effluent therefrom; (d) passing the hydrocracking zone effluent directly to the hot, high pressure stripper to produce a second vapor stream comprising lower boiling hydrocarbonaceous compounds and a second liquid stream; (e) passing at least a portion of the first vapor stream recovered in step (b) and at least a portion of the second vapor stream recovered in step (d) to a post-treat hydrogenation reaction zone; (f) condensing at least a portion of the resulting effluent from the post-treat hydrogenation zone to produce a third liquid stream comprising hydrocarbonaceous compounds boiling at a temperature below the first hydrocarbonaceous feedstock and a third vapor stream comprising hydrogen and hydrogen sulfide; (g) passing a second hydrocarbonaceous feedstock having a lower average boiling point than that of the first hydrocarbonaceous feedstock into an intermediate location in the denitrification and desulfurization reaction zone to serve as quench; (h) passing at least a portion of the third vapor stream to the hydrocracking zone; (i) passing at least a portion of the third vapor stream to the denitrification and desulfurization reaction zone; and (j) passing at least a portion of the third vapor stream to the hot, high pressure stripper.
Other embodiments of the present invention encompass further details such as types and descriptions of feedstocks, hydrocracking catalysts and preferred operating conditions including temperatures and pressures, all of which are hereinafter disclosed in the following discussion of each of these facets of the invention.